Re: [FFmpeg-devel] [PATCH] lavc/qsvenc: Set default bitrate to 2M

[Timo Rothenpieler <timo@rothenpieler.org>]

On 06/12/2023 07:51, Xiang, Haihao wrote:
> On Di, 2023-12-05 at 12:47 +0100, Timo Rothenpieler wrote:
>> On 05.12.2023 09:15, Xiang, Haihao wrote:
>>> From: Haihao Xiang <haihao.xiang@intel.com>
>>>
>>> 2M is suitable for more cases, e.g. 4K video.
>>>
>>> Signed-off-by: Haihao Xiang <haihao.xiang@intel.com>
>>> ---
>>>    libavcodec/qsvenc_av1.c   | 2 +-
>>>    libavcodec/qsvenc_h264.c  | 2 +-
>>>    libavcodec/qsvenc_hevc.c  | 2 +-
>>>    libavcodec/qsvenc_mpeg2.c | 2 +-
>>>    libavcodec/qsvenc_vp9.c   | 2 +-
>>>    5 files changed, 5 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/libavcodec/qsvenc_av1.c b/libavcodec/qsvenc_av1.c
>>> index c697845d7b..78c92c1844 100644
>>> --- a/libavcodec/qsvenc_av1.c
>>> +++ b/libavcodec/qsvenc_av1.c
>>> @@ -129,7 +129,7 @@ static const AVClass class = {
>>>    };
>>>    
>>>    static const FFCodecDefault qsv_enc_defaults[] = {
>>> -    { "b",         "1M"   },
>>> +    { "b",         "2M"   },
>>
>> Wouldn't it be better to use a constant quality option as default,
>> rather than a fixed bitrate?
> 
> Did you mean change the default bitrate control mode to CQP ? I was concerned
> about the impact to current users.

Yeah, it's technically a breaking change.
Though at least libx264 also at some point changed its default to a 
reasonable medium quality crf mode, away from a fixed, rather low, bitrate.
Not sure if that was done on a major bump, or if it was considered low 
impact enough to just push out.

>> 2M still seems incredibly low for 1080p, let alone for 4K content.
> 
> Some other HW encoders also use 2M, I'd like to use the same default value.

It's probably worth considering switching those to a crf equivalent as 
well, where possible.
It matches much more what a typical user would expect if they input a 
commandline with no further options.

> Thanks
> Haihao
> 
>>
>>>        { "g",         "-1"   },
>>>        { "bf",        "-1"   },
>>>        { "refs",      "0"    },
>>> diff --git a/libavcodec/qsvenc_h264.c b/libavcodec/qsvenc_h264.c
>>> index 071a9a79e9..37b39cb441 100644
>>> --- a/libavcodec/qsvenc_h264.c
>>> +++ b/libavcodec/qsvenc_h264.c
>>> @@ -178,7 +178,7 @@ static const AVClass class = {
>>>    };
>>>    
>>>    static const FFCodecDefault qsv_enc_defaults[] = {
>>> -    { "b",         "1M"    },
>>> +    { "b",         "2M"    },
>>>        { "refs",      "0"     },
>>>        { "g",         "-1"    },
>>>        { "bf",        "-1"    },
>>> diff --git a/libavcodec/qsvenc_hevc.c b/libavcodec/qsvenc_hevc.c
>>> index c5b7ac7cc4..181d06cb00 100644
>>> --- a/libavcodec/qsvenc_hevc.c
>>> +++ b/libavcodec/qsvenc_hevc.c
>>> @@ -374,7 +374,7 @@ static const AVClass class = {
>>>    };
>>>    
>>>    static const FFCodecDefault qsv_enc_defaults[] = {
>>> -    { "b",         "1M"    },
>>> +    { "b",         "2M"    },
>>>        { "refs",      "0"     },
>>>        { "g",         "248"   },
>>>        { "bf",        "-1"    },
>>> diff --git a/libavcodec/qsvenc_mpeg2.c b/libavcodec/qsvenc_mpeg2.c
>>> index 22f1ff7c0d..012cec3a58 100644
>>> --- a/libavcodec/qsvenc_mpeg2.c
>>> +++ b/libavcodec/qsvenc_mpeg2.c
>>> @@ -82,7 +82,7 @@ static const AVClass class = {
>>>    };
>>>    
>>>    static const FFCodecDefault qsv_enc_defaults[] = {
>>> -    { "b",         "1M"    },
>>> +    { "b",         "2M"    },
>>>        { "refs",      "0"     },
>>>        // same as the x264 default
>>>        { "g",         "250"   },
>>> diff --git a/libavcodec/qsvenc_vp9.c b/libavcodec/qsvenc_vp9.c
>>> index d0340ef94b..8658b8ec2d 100644
>>> --- a/libavcodec/qsvenc_vp9.c
>>> +++ b/libavcodec/qsvenc_vp9.c
>>> @@ -93,7 +93,7 @@ static const AVClass class = {
>>>    };
>>>    
>>>    static const FFCodecDefault qsv_enc_defaults[] = {
>>> -    { "b",         "1M"    },
>>> +    { "b",         "2M"    },
>>>        { "refs",      "0"     },
>>>        { "g",         "250"   },
>>>        { "trellis",   "-1"    },
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